1. Field of the Invention
The present invention relates to a flat panel display device, and more particularly, to a method and apparatus for fabricating a flat panel display device.
2. Discussion of the Related Art
In the current information-driven society, display devices are increasingly emphasized in importance as a visual communication medium. Cathode ray tubes or Braun tubes, which remain in the product mainstream are disadvantageous due to their large size and weight.
Flat panel display technology includes liquid crystal display (LCD) devices, field emission display (FED) devices, plasma display panel (PDP) devices, electroluminescence display (ELD) devices, and the like. Liquid crystal display devices satisfy the demand for light, thin, and small electronic products. Further, their productivity has improved. Thus, liquid crystal display devices have been rapidly replacing the cathode ray tubes in many applied fields.
An active matrix type liquid crystal display device, which drives a liquid crystal cell by use of a thin film transistor (hereinafter, “TFT”), has advantages including excellent picture quality and low power consumption. Further, it has rapidly been developed to be made with large-size and high-resolution characteristics due to mass production technology.
The active matrix type liquid crystal display device, as shown in FIG. 1, includes a color filter substrate 22 and a TFT array substrate 23 bonded together with a liquid crystal layer 15 formed therebetween. The color filter substrate 22 includes a color filter 13 and a common electrode 14 formed on the rear surface of an upper glass substrate 12. A first polarizer 11 is attached onto the front surface of the upper glass substrate 12. The color filter 13 has red (R), green (G) and blue (B) color filter layers arranged to transmit a light of a specific wavelength range, thereby enabling the display of color. A black matrix is formed between adjacent color filter layers R, G, and B.
In the TFT array substrate 23, data lines 19 and gate lines 18 cross each other on the front surface of a lower substrate 16, and a TFT 20 is formed at each intersection thereof. A pixel electrode 21 is formed at a cell area between the data line 19 and the gate line 18 on the front surface of the lower substrate 16. The TFT 20 switches a data transmission path between the data line 19 and the pixel electrode 21 in response to a scan signal from the gate line 18, thereby driving the pixel electrode 21. The second polarizer 17 is attached to the rear surface of the TFT array substrate 23.
A liquid crystal layer 15 controls the transmitted amount of light that is incident to the TFT array substrate 23 by an electric field applied thereto. The first polarizer 11 and the second polarizer 17 of the color filter substrate 22 and the TFT array substrate 23, respectively, transmit a polarized light in any one direction. When the liquid crystal layer 15 is in a 90° TN mode, the polarizing directions cross each other perpendicularly. An alignment film (not shown) is formed in contact with the liquid crystal layer 15 disposed between the color filter substrate 22 and the TFT array substrate 23.
Generally, a process of fabricating the active matrix type liquid crystal display device is divided into a substrate cleaning process, a substrate patterning process, an alignment film forming/rubbing process, a substrate bonding/liquid crystal injecting process, a mounting process, an inspection process, a repair process, and so on. The substrate cleaning process removes impurities, which contaminate a substrate surface, with a cleaning solution. The substrate patterning process is divided into a patterning process of the color filter substrate 22 and a patterning process of the TFT array substrate 23 to form the respective substrates. The alignment film forming/rubbing process spreads an alignment film over each of the color filter substrate 22 and the TFT array substrate 23, and rubs the alignment film with a rubbing cloth. The substrate bonding/liquid crystal injecting process bonds the color filter substrate 22 with the TFT array substrate 23 by use of a sealant, injects liquid crystal material through a liquid crystal injection hole, and then seals up the liquid crystal injection hole. The mounting process connects a tape carrier package (hereinafter, “TCP”) to a pad part of the substrate, wherein the TCP has an integrated circuit (IC), such as a gate drive IC, and a data drive IC mounted thereon. The IC can be directly mounted on the substrate by a chip-on-glass (hereinafter, “COG”) method as well as a tape automated bonding (hereinafter, “TAB”) method. The inspection process includes an electrical inspection that is performed after forming the pixel electrode 21 and the signal line, such as the data line 19 and the gate line 18, in the TFT array substrate 23. The electrical inspection and a macrography are performed after the substrate bonding/liquid crystal injecting process. The repair process performs a restoration of a TFT array substrate 23 that is judged to be repairable by the inspection process. A TFT array substrate 23 that is judged to be not repairable in the inspection process is disposed as waste.
In the fabricating method of most of the flat panel displays, including a liquid crystal display device, a thin film material deposited on the substrate is patterned by a photolithography process. The photolithography process is a series of photographic processes that generally include photo-resist spreading, mask aligning, exposure, development and cleaning processes. However, the photolithography process has problems. For example, time required for processing is long, photo-resist materials and strip solutions are greatly wasted, and expensive equipment, such as exposure equipment, is required.
A method and apparatus for fabricating a flat panel display device, described in U.S. patent application Ser. No. 11/154,649, filed on Jun. 17, 2005 and commonly assigned to the assignee of the present invention, is incorporated herein by reference and is briefly discussed below. In particular, FIG. 2 and FIG. 3 of the related art show a method and apparatus for fabricating a flat panel display device that form a thin film pattern by using a soft mold 134 instead of a photo-resist patterning process of the related art.
The thin film patterning process using the soft mold 134 includes a spreading process of an etch resist solution 133a on a substrate 131 provided with a thin film 132a, a patterning process of a layer of etch resist solution 133a using a soft mold 134, an etching process for patterning the thin film 132a, a stripping process for removing residual etching resist patterns, and an inspecting process.
The thin film 132a formed on the substrate 131 is formed from a base material, which is used as a metal pattern, an organic pattern, and an inorganic pattern that exist in an array of the flat panel display device on the substrate 131 by a known spreading process or deposition process. The etch resist solution 133a includes a main resin, which is one of a liquid polymer precursor, liquid monomer, an activator, an initiator, a thermal flow derivative, and the like. The etch resist solution 133a is spread over the thin film 132a by the spreading process, such as nozzle spraying, spin coating, and the like. The soft mold 134 is made of a rubber material with high elasticity such as polydimethylsiloxane (PDMS) and the like. The soft mold 134 includes a reference surface 134b and a groove 134a that is indented from the reference surface 134b. The groove 134a corresponds to a pattern to be made to remain on the substrate 131. Moreover, the groove 134a and the reference surface 134b are surface-treated to be either hydrophobic or hydrophilic. Hereinafter, an explanation will be made with respect to the soft mold 134 being hydrophobic.
The soft mold 134 is aligned on the etch resist solution 133a. The soft mold 134 is applied to the etch resist solution 133a with pressure with which the soft mold 134 can only be in contact with the thin film 132a, i.e., a pressure of only about its own weight. For example, the etch resist solution 133a, as shown in FIG. 3, moves into the groove 134a of the soft mold 134 by a capillary force that is generated by a pressure between the soft mold 134 and a glass substrate 131, and a repulsive force between the reference surface 134b and the etch resist solution 133a. As a result, the etch resist pattern 133b is formed on the thin film 132a in a pattern shaped by the groove 134a of the soft mold 134. After the soft mold 134 is separated from the substrate 131, a wet etching process or a dry etching process is performed. During the etching process, the etch resist pattern 133b acts as a mask. Thus, only the thin film 132a covered by the etch resist pattern 133b remains on the substrate 131 and the other exposed portions of the thin film 132a are removed. Subsequently, the etch resist pattern 133b is removed by the stripping process. Whether there is a short circuit or a broken wire from the thin film pattern 132b is then determined by electrical and optical inspections of the thin film pattern 132b. After the soft mold 134 is separated from the substrate 131, the soft mold 134 is cleaned by an ultraviolet ray and ozone O3, and is reused in the patterning process of another thin film 132a. 
A method of fabricating the soft mold 134 shown in FIG. 2 and FIG. 3 is explained as follows. As shown in FIG. 4, a molding material 135, which includes polydimethylsiloxane and a small amount of curing agent, is coated on a master mold 184 provided with at least one pattern 182 of a photo-resist pattern and inorganic pattern on a substrate 180. At this stage, the molding material 135 is in a liquid polymer precursor state. After the molding material 135 is hardened by an ultraviolet ray hardening or a heat hardening process, the hardened molding material 135 is separated from the master mold 184 to form the soft mold 134 having the reference surface 134b and the groove 134a. 
The thin film pattern 132b is formed by using the above-mentioned soft mold 134, so that it becomes possible to simplify the fabricating process of the flat panel display device in comparison to the related art photographic process. However, because the soft mold 134 formed by the above-described description is soft, a central area of the groove 134a sags when the area of the groove 134a (i.e., the area indented from the reference surface 134b) is wide. In other words, as shown in FIG. 5, if an area d2 of the groove 134a is relatively wider than an area d1 of the reference surface 134b, then the central area of the groove 134a sags in the vertical direction such that the desired etch-resist pattern 133b is not formed. Accordingly, the etch-resist pattern 133b may not be formed uniformly.